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PERF: Index.__getitem__ should not need to do dtype inference #31903

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jorisvandenbossche opened this issue Feb 11, 2020 · 3 comments
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PERF: Index.__getitem__ should not need to do dtype inference #31903

jorisvandenbossche opened this issue Feb 11, 2020 · 3 comments
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Indexing Related to indexing on series/frames, not to indexes themselves Performance Memory or execution speed performance

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@jorisvandenbossche
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Currently, the __getitem__ call in a snippet like

idx = pd.Index([1, 2, 3, 4])
idx[np.array([0, 3])]

does type inference when creating the new Index object (using _shallow_copy_with_infer), while I think we can always know for sure the result will be another Int64Index (for the above example) ?
@jorisvandenbossche jorisvandenbossche added Indexing Related to indexing on series/frames, not to indexes themselves Performance Memory or execution speed performance labels Feb 11, 2020
@jorisvandenbossche jorisvandenbossche added this to the Contributions Welcome milestone Feb 11, 2020
@jorisvandenbossche jorisvandenbossche mentioned this issue Feb 11, 2020
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@jbrockmendel
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Index.__getitem__ no longer uses _shallow_copy_with_infer. Are there other optimizations you had in mind?

@jbrockmendel
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Closing as I'm pretty sure this no longer does type inference. Feel free to reopen if ive got this wrong.

@jorisvandenbossche jorisvandenbossche removed this from the Contributions Welcome milestone Jun 10, 2020
@jorisvandenbossche
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Yep, that's correct

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Indexing Related to indexing on series/frames, not to indexes themselves Performance Memory or execution speed performance
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@jorisvandenbossche @jbrockmendel